Vinylidene fluoride (VDF) resins are endowed with outstanding mechanical properties within a broad range of temperature and excellent resistance to high temperature, to organic solvents and to various chemically aggressive environments.
Thanks to their properties, these resins are advantageously used for manufacturing articles such as electrodes and/or separators for use in secondary batteries, especially in Lithium ion batteries.
For instance, WO 2008/129041 (SOLVAY SOLEXIS S.P.A.) 30 Oct. 2008 discloses a linear semi-crystalline vinylidene fluoride (VDF) copolymer with 0.05-10% by moles of a (meth)acrylic monomer, wherein recurring units derived from (meth)acrylic monomers are randomly distributed throughout the whole vinylidene fluoride backbone, and use thereof for manufacturing electrodes and/or separators. Solvents commonly used for dissolving these VDF copolymers typically include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate and trimethyl phosphate.
Also, EP 1621573 A (KUREHA CORPORATION) 1 Feb. 2006 discloses porous membranes prepared by a composition comprising a vinylidene fluoride (VDF) copolymer with 0.01-10% by moles of a monomer having at least one group selected from an epoxy, a hydroxyl, a carboxyl, an ester, an amide and an acid anhydride group, a plasticizer and a suitable solvent. Representative embodiments of this document relate to hollow porous fiber membranes prepared by compositions of these copolymers in N-methyl-2-pyrrolidone.
Further, US 2002/0197536 (SAMSUNG SDI CO. LTD.) 26 Dec. 2002 discloses a polymeric electrolyte for use in Lithium batteries comprising a vinylidene fluoride (VDF) copolymer with hexafluoropropylene or a copolymer further comprising recurring units of at least one compound selected from the group consisting of acrylic acid and maleic acid monoalkylester. Representative embodiments of this document relate to electrolytic solutions of these copolymers in N-methyl-2-pyrrolidone.
Nevertheless, due to certain environmental concerns, methods wherein components of a secondary battery such as electrodes and/or separators made of VDF polymers are manufactured using alternative solvents having a more favourable toxicological profile are attracting increased attention.
There is thus still a need in the art for a process for manufacturing components of a secondary battery such as electrodes and/or separators made of VDF polymers which advantageously enables avoiding use of toxic and polluting solvents and thus eliminating cost, safety and environmental concerns related to handling of large volume of said solvents.